Characterization of photocatalytic materials used for water treatment
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As the pressure on water bodies throughout the world is increasing, good water qualityobtained through water treatment is essential to secure health and welfare of the population. Many chemical compounds used in industry and agriculture with discharge todrinking water sources or vulnerable recipients have not been examined properly beforeapproval.Many of these chemicals have eventually been considered to be toxic or hostile towardsthe environment, hence they are called micro-pollutants. Some of the newly discoveredmicro-pollutants are also known as emerging contaminants, but this is certainly not awell-defined group of species (K¨ummerer 2011), even though it is frequently reported inscientific papers.Examples of such compounds are pharmaceuticals, dyes, personal care products, soapsand pesticides. Actually, some of them threaten to destroy water sources and other aquaticenvironments.Unfortunately, conventional treatment methods are not designed to remove micropollutants. However, so-called advanced oxidation processes (AOPs) are up-and-comingwater treatment processes that are promising for this matter. In this thesis one of themost well-known, but least understood AOPs are examined. It is called photocatalysiswith the use of TiO2 and UV-LED.Further, experiments designed to find the bandgap of a large selection of materials ofmodified TiO2 have been conducted for this thesis. The modification has been conductedthrough doping with metal ions. Some of the most promising materials from the bandgapexperiments were put in a photoreactor to find the radical production compared to areference TiO2 material.The results from the bandgap analyses showed that most of the materials had decreasedbandgap compared to the reference at 3.16 eV. In particular, the manganese-doped TiO2materials showed the highest decrease, down to 2.89 eV for one of the samples.Meanwhile, the radical production experiments had some promising results, but asduplicates and triplicates of the experiments were executed, none of them were reproducible. In other words, the results from the radical production were not valid and couldtherefore not be used for extensive discussion.Furthermore, this made large parts of the master thesis pointless, since the radicalproduction is a substantial part of the process. For the future work in the project, theexperiments and the revealed weaknesses may, however, contribute to a better setup andprocedure for further testing.